Re: bug#23750: 25.0.95; bug in url-retrieve or json.el

[Philipp Stephani <p.stephani2@gmail.com>]

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Eli Zaretskii <eliz@gnu.org> schrieb am Mi., 28. Dez. 2016 um 19:28 Uhr:

> > From: Philipp Stephani <p.stephani2@gmail.com>
> > Date: Wed, 28 Dec 2016 18:09:52 +0000
> > Cc: larsi@gnus.org, dgutov@yandex.ru, kentaro.nakazawa@nifty.com,
> >       emacs-devel@gnu.org
> >
> >
> > [1:text/plain Show]
> >
> >
> > [2:text/html Hide Save:noname (9kB)]
> >
> > Eli Zaretskii <eliz@gnu.org> schrieb am Mi., 30. Nov. 2016 um 19:45 Uhr:
> >
> >  > From: Philipp Stephani <p.stephani2@gmail.com>
> >  > Date: Wed, 30 Nov 2016 18:23:14 +0000
> >  > Cc: dgutov@yandex.ru, kentaro.nakazawa@nifty.com, emacs-devel@gnu.org
> >  >
> >  > > Yes, this is not a json.el problem at all. It does the correct
> thing,
> >  > > and shouldn't be changed.
> >  >
> >  > ??? Why should any code care whether a pure-ASCII string is marked as
> >  > unibyte or as multibyte? Both are "correct".
> >  >
> >  > I guess the problem is that process-send-string cares. If it didn't,
> we wouldn't have the problem.
> >
> >  I don't think I follow. The error we are talking about is signaled
> >  from url-http-create-request, not from process-send-string.
> >
> > Yes, but url-http-create-request only cares about unibyte strings
> because the request it creates is passed to
> > process-send-string, which special-cases unibyte strings.
>
> How do you see that process-send-string special-cases unibyte strings?
>

The send_process function has two branches, one for unibyte, one for
multibyte.


>
> >  > For URL, we'd need functions like
> >  > (byte-array-length s) = (length (string-to-unibyte s))
> >
> >  Why do you need this? string-to-unibyte is well-defined only for
> >  unibyte or ASCII strings (if we forget the raw bytes for a moment), so
> >  length will do.
> >
> > We need it because we have to send the byte length in a header. We can't
> just use (length s) because it
> > would silently give a wrong result.
>
> We are miscommunicating.  string-to-unibyte can only meaningfully be
> called on a pure-ASCII string, and for pure-ASCII strings 'length'
> will count bytes.  So I see no need for 'byte-array-length' if its
> implementation is as you indicated.
>

That depends on how you want to represent byte arrays/octet streams in
Emacs. If you want to represent them using unibyte strings, then you indeed
only need `length'. But some earlier messages sounded like you wanted to
represent byte arrays either using unibyte strings or byte-only multibyte
strings. In that case `string-to-unibyte' is necessary.


>
> >  > (process-send-bytes s) = (process-send-string (string-to-unibyte s))
> >
> >  Why is this needed? process-send-string already encodes its argument,
> >  which produces a unibyte string.
> >
> > We can't give a multibyte string to process-send-string, because we have
> to pass the length in bytes in a
> > header first. Therefore we have to encode any string before passing it
> to process-send-string.
>
> Once you encoded the string, why do you need anything except calling
> process-send-string?
>
>
The byte size should be added as a Content-length HTTP header. If
url-request-data is a unibyte string, that's not a problem (except for the
newline conversion behavior in send_string), you can just use `length'. But
if it's a multibyte string, you need to encode first to find the byte
length.

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